The national science academies of all the G8 countries issued an unprecedented challenge to their governments on Tuesday, urging immediate action to curb greenhouse gas emissions to fight global warming.

Scientific evidence about the causes and impacts of climate change is now so clear that effective measures to address them can no longer be delayed, the elite institutions said.

The call for firm steps to be agreed at the Gleneagles summit next month puts further pressure on US President Bush to sign up to binding emissions controls, particularly as his own country's National Academy of Science (NAS) is among the signatories.

The strongly worded statement was also endorsed by the government-sponsored research academies of China, India and Brazil, offering the strongest indications yet that major developing countries are serious about reducing their own contributions to global warming.

A lack of targets for the developing world was one of the key objections cited by the Bush administration when it withdrew from the Kyoto Protocol on climate change in 2001.

The academies also reject another important American argument: that the science of climate change is not yet sufficiently certain to justify action. "The scientific understanding of climate change is now sufficiently clear to justify prompt action," the statement said. "It is vital that all nations identify cost-effective steps that they can take now, to contribute to substantial and long-term reduction in net global greenhouse gas emissions."

While it accepted that climate science will always carry an element of uncertainty, it said: "A lack of full scientific certainty about some aspects of climate change is not a reason for delaying an immediate response that will, at a reasonable cost, prevent dangerous anthropogenic interference with the climate system."

The agreement of the Russian Academy of Sciences is also significant, as its members, who have previously been more sceptical of the science of global warming than the other institutions, last year advised President Putin not to ratify the Kyoto Protocol.

Lord May of Oxford, President of the Royal Society, attacked the US position on global warming as "misguided," pointing out that Bush had repeatedly overruled his own scientists' advice. "President Bush has an opportunity at Gleneagles to signal that his administration will no longer ignore the scientific evidence and act to cut emissions," he said. "It is clear that world leaders, including the G8, can no longer use uncertainty about aspects of climate change as an excuse for not taking urgent action to cut greenhouse gas emissions.

"Significantly, along with the science academies of the G8 nations, this statement's signatories include Brazil, China and India, who are among the largest emitters of greenhouse gases in the developing world."

Tony Blair has pledged to use Britain's G8 presidency to make climate change a priority at the summit. While US participation in the Kyoto accord remains unlikely, the prime minister remains hopeful that President Bush might agree to long-term emissions controls if countries such as China and India also sign up. But China has already signed up the Kyoto Protocol.

The Kyoto Protocol, which was signed in 2000, demands an average 5.2 per cent cut in emissions by 2010 from developed nations, taking 1990 figures as a baseline. Developing countries were explicitly excluded from any targets, as the industrialized world has made by far the largest historical contribution to greenhouse gases.

US objections to this predate the Bush administration in 1999, the Senate voted 95-0 to reject any global warming treaty that did not include developing countries and had the potential to harm the American economy.

Its position has hardened since Bush's election, particularly in light of industrial competition from developing countries.

The US is also more heavily reliant than European countries on coal, which generates more greenhouse gases.

(China Daily 06/09/2005 page6)